usb: dwc3: clear 'res_trans_idx' as soon as it becomes invalid

Transfer resource index is cleared in hardware when XFERCOMPLETE
event is generated, so clear the driver's res_trans_idx variable
immediately after that event is received. The upcoming hibernation
patches depend on this change.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 4fa2c98..73efdf6 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -617,6 +617,7 @@
 	struct dwc3_ep		*dep = dwc->eps[event->endpoint_number];
 
 	dep->flags &= ~DWC3_EP_BUSY;
+	dep->res_trans_idx = 0;
 	dwc->setup_packet_pending = false;
 
 	switch (dwc->ep0state) {